CVE-2023-39975Network attack vector

Authenticated KDC denial of service via aliased pointer

Published Aug 16, 2023 · Updated Feb 25, 2026

Double free in MIT Kerberos 5 1.21 allows remote authenticated users to interrupt the KDC through a TGS renew or validate request. In tgs_issue_ticket(), copying the entire header ticket aliases its enc_part pointer to the new ticket until encryption; if handle_authdata() fails, cleanup frees the same pointer twice. Reachability requires valid Kerberos credentials and an authorization-data handling failure, resulting in denial of ticket-granting service.

CVSS severity8.8
High
EPSS probability1.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double free in MIT Kerberos 5 1.21 allows remote authenticated users to interrupt the KDC through a TGS renew or validate request. In tgs_issue_ticket(), copying the entire header ticket aliases its enc_part pointer to the new ticket until encryption; if handle_authdata() fails, cleanup frees the same pointer twice. Reachability requires valid Kerberos credentials and an authorization-data handling failure, resulting in denial of ticket-granting service.

The record

CVE
CVE-2023-39975
Published
Aug 16, 2023
Updated
Feb 25, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-415, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 16, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
8.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-415Double Free
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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